Switchable Iodine Adsorption Management in Polyoxovanadate-Cucurbit[6]uril-Based Supramolecular Framework Materials

The upsurge of precision chemistry has put forward higher demands for material synthesis, along with the shift of research focus from structural assembly to the spatial arrangement of molecules in a desired manner. Herein, polyoxovanadates (POV) have been hired for regulating the distribution status of cucurbit[6]urils (CB[6]) in their coconstructed supramolecular frameworks. The outer-surface bindings between POV and CB[6] via noncovalent forces contribute greatly to improving the accessibility of macrocycles and stability of entire architectures. In this context, pyridine (py) and ethylenediamine (en) have been allowed to enter the pocket of CB[6], resulting in the respective host-guest complexes. Upon that, the distinct iodine adsorption performances of the as-made frameworks have been observed and analyzed. Supported by both experimental and theoretical data, it has been revealed that the smooth electron delivery from en to CB[6] could promote the ionization of I2 -> I3 -, thereby enhancing the adsorption efficiency significantly. By contrast, the encapsulated py prefers to weaken the electron supply of CB[6], thus blocking the reduction of iodine and quenching the adsorptive ability. As a result, the capture of iodine by such adsorbents can be switched on or off by altering the electron transfer routes within the host-guest systems.